Oriented strand board, parallel strand lumber and other engineered wood products produced from discrete wood elements are produced in a press by depositing a mat of resin coated wood elements within the press and applying a compressive force to the mat. Heat from a variety of sources is added to substantially cure the resin while the mat is within the press. The heat may be added in the form of microwave energy, conduction, radio frequency energy, steam injection or the like.
As depicted in FIG. 1, current press systems include a pair of opposed platens 40a configured to continuously compress a material 38a into a desired shape. Adjacent each platen 40a is a press belt 37 running on a roller arrangement 35. The belt 37 and roller arrangement 35 combination allows movement of the material 38a through the platens 40a while the platens are continuously applying a compressive force to the material 38a. This method of forming a composite wood product is problematic in many ways.
The current continuous press designs impede the application of energy. The press belt, bearing arrangements and necessary lubrication materials represent a significant barrier for the application of heating energy to the product. The heating of the product via a hot platen technology results into an uneven heating profile.
FIG. 2 show a conventional heating profile of a hot platen press. Chart 15 reflects temperature and pressure within the material 38b with respect to temperature in degrees Celsius on the Y-axis 17 and time in seconds on the X-axis. This chart 15 is taken from a graduate thesis prepared by Stephen E. Johnson at Virginia Polytechnic Institute and State University, Blacksburg, Va., in August 1990. The thesis was entitled “Response of Mat Conditions and Flakeboard Properties to Steam-Injection Variables.”